The Pediatric AIDS Clinical Trials Group (PACTG) is the preeminent organization in the world for evaluating treatments for HlV-infected children and adolescents, and for developing new approaches for the interruption of mother-to-infant transmission. It has set the standards of care for children infected with HIV and for the interruption of vertical transmission. The PACTG is a multicenter, multidisciplinary investigative group. This cooperative agreement concerns the PACTG Coordinating and Operations Center (CORC), which includes support for the Group Leader, the Executive Committee, Other standing committees, a Community Constituency Group, the Operations Center, and the core and developmental laboratories. Associated with the CORC, under separate applications, are 18-25 pediatric AIDS Clinical Trials Units and a Statistical and Data Management Center. The Group will be managed by an Executive Committee which will oversee an integrated research agenda developed by four Research Agenda Committees (Perinatal Transmission, primary Therapy, Opportunistic Infections, and Immunology/Immune-Based Therapy (IBT)], three Scientific Committees (Virology, Immunology, and Pharmacology), and five Resource Committees (Neurology/Neuropsychology, Adolescent, Community Constituency Group, Supportive Care/Quality of Life, and Site Advisory Core Committee). The scientific agenda of the PACTG encompasses the critical issues that impact mother-to-infant transmission and treatment of HIV-infected children and adolescents. The three primary goals of the PACTG's scientific agenda are (l) to decrease mother-to-infant transmission of HIV to less than 2%, (2) to achieve a 90% 10-year survival for children perinatally infected with HIV, and (3) to develop novel strategies for early treatment of newly-infected infants and adolescents. The structure of the PACTG has been designed to provide a mechanism for a coordinated response to rapidly changing investigative opportunities for HIV-infected infants, children, adolescents, and pregnant women.